Switching power converters provide regulated output voltages for numerous electronic products including lamps, such as light emitting diode and gas discharge type lamps, cellular telephones, computing devices, and personal digital assistants. Power converters, such as switching power converters, include an inductor that may be magnetized and used to drive current to generate a regulated output voltage for an end component, such as a speaker of a mobile device. However, the inductors have current limits and exceeding the current limit can be hazardous. Conventionally, current limits are enforced by detecting that the current exceeds a particular threshold and then disconnecting the inductor from a source. However, there is often a delay in disconnecting the inductor that causes the inductor current to still exceed the threshold.
FIG. 1 is one example of a conventional technique for limiting peak current according to the prior art. A line 102 indicates an inductor current. The current is ramping up and at time 112 crosses a threshold current value Ipk,th shown as line 120. At time 114, the controller may detect that the threshold current value Ipk,th is crossed after a delay t1 from the actual crossing at time 112. Circuitry may then generate control signals that cause a switch to disconnect the inductor from the source to terminate the current ramping in the inductor. After a delay t2, the inductor is disconnected at time 116. As a result of the delays t1 and t2, shown as a total td, the actual inductor current exceeded the peak current threshold Ipk,th by an amount ΔI. The ΔI amount may cause the inductor current to exceed safe operating ranges, and thus generate hazardous conditions.
Another conventional solution is to compensate for the delay td by predicting when time 112 will occur. FIG. 2 is another example of a conventional technique for limiting peak current according to the prior art. The inductor can be disconnected at time 212, approximately delay time td before the peak current threshold of line 120 is reached. However, this prediction technique can be inaccurate as there are other unknowns and parameters that can be difficult to predict. Further, to ensure the threshold current does not exceed the safe limits, the inductor must be operated conservatively by predicting peak current times much earlier than expected. However, this results in extremely conservative operation of the inductor and does not allow the inductor to operate at full scale. In fact, prediction errors may be as much as or more than 30%. A prediction with 30% error and resulting safety buffer results in significant under operation of the inductor.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for power converters employed in consumer-level devices, such as mobile phones. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art.